For actual Differential-signaling (DS) techniques such as low-voltage differential-signaling (LVDS), the ideal balance or symmetrical topology cannot be established, and hence, an imbalance component is excited in practical high-density packaging systems. In this paper, we newly attempt to identify and quantify the frequency responses of the imbalance component and electromagnetic (EM) radiation from asymmetrical differential-paired lines, using a physics-based model, which is constructed with an equivalent circuit model to calculate current distribution, and radiation model based on Hertzian dipole antenna. The physics-based model is validated by comparing the predicted results with FDTD simulation. The frequency response of EM radiation from asymmetrical differential-paired lines can be identified using our proposed model. This study has successfully established a basic method to effectively predict EM radiation from practical differential-paired lines.